CODASYL network model

CODASYL network model The data model proposed by the CODASYL DBTG (see CODASYL) in which data is organized into records of different types and records are organized into sets of different types, both record and set types being named. A particular set type is defined as having an owner record type and one or more member record types. An instance of a set type consists of a single instance of its owner record type and zero, one, or more instances of each of its member record types. A member record instance may not occur in more than one instance of a particular set type.

In practice sets usually have only one member record type when, in effect, the CODASYL network model provides for a one–many relationship between the two types of records to be maintained, modeled as an isomorphism between the owner record instances and the elements of a disjoint partition of the member record instances. A set is said to be mandatory if this partition is constrained to be a complete cover and optional if it need not be. A common way of implementing database systems based on this model is by pointers embedded in the records, but pointers and this implementation technique are not inherent to the model, which is formulated in terms of abstractions.

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CODASYL

CODASYL An organization dedicated mainly to the development of the data processing language Cobol and associated software. It originated at a meeting, the Conference on Data Systems Languages, called in the Pentagon by the US Department of Defense in 1959 to consider both the desirability and feasibility of establishing a common language for data processing. The acronym for that conference, CODASYL, became the name of the continuing organization. The initial version of the language, COBOL-60, was published the following year, subsequent versions being COBOL-61, COBOL-65, and the Cobol ANSI standards in 1968, 1974, and 1985, adopted by ISO.

During 1965–67 CODASYL established a Database Task Group (DBTG) to investigate and develop proposals for a common database management system to be used in association with Cobol as the host language (see database language). In 1969 a report giving a specification was published and widely discussed. A revised report published in 1971 allowed also for other languages to be used as the host programming language. IDMS is the leading product based on these proposals. See CODASYL network model.

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